linux-cve-announce - CVE-2025-21958: Revert "openvswitch: switch to per-action label counting in conntrack"

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Message-ID: <2025040144-CVE-2025-21958-c94c@gregkh>
Date: Tue,  1 Apr 2025 16:45:43 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21958: Revert "openvswitch: switch to per-action label counting in conntrack"

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

Revert "openvswitch: switch to per-action label counting in conntrack"

Currently, ovs_ct_set_labels() is only called for confirmed conntrack
entries (ct) within ovs_ct_commit(). However, if the conntrack entry
does not have the labels_ext extension, attempting to allocate it in
ovs_ct_get_conn_labels() for a confirmed entry triggers a warning in
nf_ct_ext_add():

  WARN_ON(nf_ct_is_confirmed(ct));

This happens when the conntrack entry is created externally before OVS
increments net->ct.labels_used. The issue has become more likely since
commit fcb1aa5163b1 ("openvswitch: switch to per-action label counting
in conntrack"), which changed to use per-action label counting and
increment net->ct.labels_used when a flow with ct action is added.

Since there’s no straightforward way to fully resolve this issue at the
moment, this reverts the commit to avoid breaking existing use cases.

The Linux kernel CVE team has assigned CVE-2025-21958 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.12 with commit fcb1aa5163b1ae4cf2864b688b08927aac51f51e and fixed in 6.12.20 with commit 9e79fdabd52cfce1a021640a81256878a2c516a2
	Issue introduced in 6.12 with commit fcb1aa5163b1ae4cf2864b688b08927aac51f51e and fixed in 6.13.8 with commit d91bfc64a4886102746e74d2c6f3a61e9a77fd7d
	Issue introduced in 6.12 with commit fcb1aa5163b1ae4cf2864b688b08927aac51f51e and fixed in 6.14 with commit 1063ae07383c0ddc5bcce170260c143825846b03

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21958
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/openvswitch/conntrack.c
	net/openvswitch/datapath.h

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9e79fdabd52cfce1a021640a81256878a2c516a2
	https://git.kernel.org/stable/c/d91bfc64a4886102746e74d2c6f3a61e9a77fd7d
	https://git.kernel.org/stable/c/1063ae07383c0ddc5bcce170260c143825846b03